JP2018534573A - Digital sensor - Google Patents

Abstract

The hybrid electronic detection component comprises an integrated circuit attached to an analog circuit in which at least one detection element is integrated. The hybrid detection component provides a digital output in response to a quantifiable change in its environmental state. Since the detection function is separated from the data processing, the influence of self-heating due to power consumption in the processor is reduced.

Description

  The present invention relates to an environment detection apparatus and a method for manufacturing such an apparatus.

  In particular, the invention relates to a composite electronic component that monitors changes in environmental conditions by changing the electrical resistance of one of its sub-components and communicates environmental condition values digitally to external electronic circuitry. Of particular interest is temperature monitoring and communication, which has great demands in all aspects of life across all market sectors, from the transport and storage of fresh food to industrial process monitoring and medical care.

  Temperature sensors with digital outputs, often referred to as “on-chip sensors”, are well known in the art and are available as a single integrated circuit or integrated into a larger integrated circuit such as a microprocessor. ing. The main function of such a sensor is generally to monitor the internal temperature of the microprocessor. In general, this type of internal sensor comprises a small semiconductor junction with a high conductance, which depends on the temperature of the junction. Digital sensors known in the art are undesirable when used to measure the temperature of an external body or external environment.

  One problem with on-chip sensors is that the high current density through the junction causes strong local self-heating and worsens the worse the heat conduction away from the junction. This causes an erroneous measurement of the temperature that is significantly higher than the actual temperature of the object being monitored.

  Another factor affecting the response of a digital temperature sensor is its physical size, particularly its high thermal mass compared to its contact area, and the thermal coupling of the monitored object.

  A preferred method of measuring temperature by electrical measurement is to use a component whose electrical resistance varies with temperature, such as a thermistor. Printed thermistors can be manufactured with high electrical resistance, often exceeding 1 MΩ or even several hundred MΩ, resulting in very low current through the device, very low power consumption, and self- Fever does not occur effectively. A further advantage of using a printed thermistor is that when printed on a thin substrate, its thermal mass is low with respect to its area and good thermal coupling can be achieved over a large area. Thus, faster response times and more accurate measurements are possible.

  Nevertheless, for many applications, digital temperature sensors are preferred for ease of use and convenience compared to conventional analog components such as thermistors. Of particular benefit is the direct output of calibrated digital values against temperature in units such as Celsius and Fahrenheit, which is meaningful to the user.

  Accordingly, it is an object of the present invention to provide an electronic component that monitors environmental conditions such as temperature and communicates the results, all the advantages of providing a calibrated digital value in the monitored condition, and a printed thermistor. Is to produce an electronic component having the technical advantages of The same configuration is also applicable to other environmental monitoring where resistance sensors can be applied, such as humidity or pressure.

  According to one aspect of the present invention, there is provided an electronic detection component that provides a digital output in response to a quantifiable change in environmental conditions, wherein at least one of the resistances changes in response to a change in environmental conditions. An analog circuit in which a detection element is integrated; at least one other resistor whose resistance remains constant even when an environmental state changes; and at least one integrated circuit, wherein a potential difference is applied to the analog circuit. The analog circuit and the integrated circuit are connected such that two potentials are applied to the input terminals of the integrated circuit, one of the two potentials corresponding to the environmental condition being measured, The other of the two potentials corresponds to a reference value and generates a unique digital signal at one or more output terminals of the integrated circuit, the unique digital signal corresponding to a change in the measured environmental condition.

  In one embodiment of the present invention, the detection element is a thermistor having a negative temperature coefficient, and the resistance of the thermistor decreases as the temperature increases.

  Preferably, at least the thermistor and wiring of the analog circuit are made by printing.

  In one embodiment of the present invention, two resistors having a constant value are connected in series to the detection element, and two potentials applied to the input of an integrated circuit are respectively connected to both ends of the one resistor having a constant value. And a potential difference across the resistor and the sensing element of a constant value.

  In one embodiment of the invention, one or more potentials are applied to a single analog-to-digital converter via an independent analog-to-digital converter or multiplexer.

  In one embodiment of the invention, the integrated circuit comprises a microcontroller or microprocessor that performs additional calculations on the data before providing the digital value to one or more output terminals.

  In some embodiments of the invention, the digital output is provided via a serial interface.

  In one embodiment of the invention, the digital output is provided through a parallel interface that uses multiple output terminals simultaneously.

  The output of one integrated circuit in one embodiment is connected to a second integrated circuit having a non-volatile memory.

  In one embodiment of the invention, the microcontroller is connected to or integrated with a radio transceiver integrated circuit and an antenna is connected to or incorporated into the analog circuit.

  The present invention will now be described in detail by way of example only and with reference to the accompanying drawings.

1 is a schematic diagram of a first embodiment of a hybrid electronic digital sensor of the present invention including an analog electronic circuit having an integrated resistance sensor fabricated on a substrate on which the digital electronic integrated circuit is mounted. FIG. FIG. 4 is a schematic diagram of a second embodiment of the hybrid electronic sensor of the present invention that can function independently of an external electronic circuit with the addition of a digital non-volatile memory and a rechargeable battery. 1 is a schematic diagram of a wireless sensing system including a hybrid electronic sensor in which an analog portion is integrated with an antenna on the same substrate and a wireless transceiver is attached for communication with the outside. 2 is a photograph of a hybrid digital electronic temperature sensor manufactured in accordance with one embodiment of the present invention.

  Simply put, the present invention is a reversal of the “sensor concept” on a chip to produce a “sensor on chip” having the same functionality but superior performance over the prior art. Such a device is necessarily a hybrid electronic detection component in which the integrated circuit is attached to an analog circuit in which at least one detection element is integrated. The hybrid detection component provides output in digital form in response to quantifiable changes in its environmental conditions.

  Functionally, however, detection is separated from data processing, reducing the effects of self-heating due to power consumption within the processor. This separation of the two functions within the composite component further allows the sensor to be designed to have a shape and performance suitable for a particular application. The resistance of the detection element changes in response to environmental changes such as temperature. Since the resistance cannot be measured directly, the sensing element is incorporated into the analog portion of the component, along with at least one other resistor that remains constant despite environmental changes. These are connected such that when a potential difference is applied to the analog circuit, two potentials are applied to the input of the integrated circuit, one corresponding to the state being measured and the other corresponding to the reference value.

  The integrated circuit generates a unique digital signal that corresponds to the combination of the two potentials, and thus corresponds to the monitored environmental condition. This unique digital signal can be as simple as the ratio of the two potentials, or, for example, temperature in degrees Celsius, force in Newtons, relative humidity in%, It may be the result of applying a complex calibration function to obtain meaningful quantities in precise units.

  Referring to the illustrated embodiment of the present invention, an analog detection circuit 1 is fabricated on a substrate 2 in the first embodiment shown in FIG. The substrate may be a sheet material or may form part of the body of the object whose environment is detected.

  In the case of a substrate formed from sheet material, the sheet may be rigid or flexible and may be a solid film, a fibrous material that may be woven or non-woven, or a composite of a combination of such materials. . Suitable solid films include the following. Polymers such as, but not limited to, polyethylene terephthalate (commonly known as PET or polyester), polyethylene naphthalate (PEN), polyimide (PI, Kapton, Vespel); these, including aluminum, iron, copper and alloys thereof Metal foils not limited to; amorphous oxides and silicates, commonly referred to as glass; single crystal and polycrystalline semiconductor materials such as silicon; sintered ceramic materials. The fiber material is generally referred to below. Paper including cellulose fibers of plant origin; synthetic polymer fibers such as polyester, polyamide, polyimide; glass fibers and ceramic fibers; including but not limited to cellulose, keratin, polyester, polyimide, polyamide, and aramid Woven or non-woven fabrics including, but not limited to, natural fibers of animal or plant origin, synthetic polymer fibers, glass fibers or ceramic fibers.

  The composite material may include, for example, a fiber composite comprising a woven or nonwoven fabric reinforced with a solidified polymer resin or a polymer filled with a fibrous or granular filler material. Alternatively, the composite material may be formed from layers of different sheet materials as described above, the orientation of which may be parallel or perpendicular to the surface of the substrate, It may be inclined at any other angle. In general, as is well known in the art, the latter structure is used to alter the mechanical properties of the sheet material, e.g. to increase stiffness or strength, but aligning the layers parallel to the surface Most often used to surface different materials. Examples of such include, but are not limited to: insulating layers applied to the conductive surface of a metal sheet, or materials deposited during the manufacture of the present invention, such as inks and adhesives. A surface coating applied to a polymer film to improve adhesion.

  An example where the substrate forms part of the body of the object is like a sensor system incorporated in the instrument housing or case. Alternatively, such a system can be integrated as part of a larger electronic circuit, in which case the substrate becomes the circuit board of the device.

  The analog circuit 1 is preferably manufactured by one of the methods generally described as printing by practitioners in the electronics manufacturing, graphics, and media and communications industries. Printing includes, but is not limited to, gravure printing, pad printing, flexographic printing, letterpress printing, offset lithography, ink jet printing, and aerosol jet printing. Alternatively, some or all of the circuit may be manufactured by other coating and deposition techniques known in the industry as described above. Other coating and deposition techniques may use photolithography, imprint lithography, or manufacture masks in combination with deposition techniques such as chemical vapor deposition, physical vapor deposition, spin coating, blade coating or slot die coating. Although it includes similarly, it is not limited to this.

  The analog circuit comprises a conductor pattern 3 that forms internal circuit connections called interconnections or wiring. The conductor pattern has connection pads 4 that are used for mounting and connecting individual components. Individual components include additional electronic components such as resistors, capacitors, diodes, etc. that form part of the overall component in the integrated circuit 5. The conductor pattern further has another connection pad 6 that functions as an external connection or terminal to the component, for example for power supply and data transfer.

  An important aspect of the present invention is that the resistance sensor element 7 is integrated in the analog circuit 1. In the sense of the present invention, the term “integrated” means that the sensor 7 is connected to the conductor pattern 3 using the same manufacturing process with at least one manufacturing step common to the manufacture of both the conductor pattern 3 and the sensor element 7. It means that it is manufactured on the same substrate 2. The description of the resistance of the sensor element 7 means that its electrical resistance changes in relation to its immediate environmental changes. In the preferred embodiment, the sensor element 7 functions as a negative temperature coefficient (NTC) thermistor whose electrical resistance decreases as the temperature increases. Preferably, the sensor 7 is manufactured by printing silicon ink on a conductive pattern, as described in US Pat. No. 9,029,180, incorporated herein by reference. Without limitation, an integrated negative temperature coefficient thermistor is either a positive temperature coefficient thermistor whose resistance increases with increasing temperature, or the resistance linearly with increasing temperature, such as platinum, for example. It may be replaced by a metal film resistor that functions as an increasing RTD (resistance temperature device). Other sensor elements that can be similarly integrated include, but are not limited to, humidity sensors or chemical sensors made from materials that change conductivity in the presence of moisture or certain target chemicals, and Pressure sensors or strain sensors made from piezoresistive materials.

  Furthermore, the analog circuit 1 comprises at least a second resistor 8 and preferably a third resistor 9. Resistor 8 and resistor 9 are fixed or constant in the sense that their electrical resistance does not change significantly even when an environmental change is sensed. For example, if the sensor element 7 is an NTC thermistor, the resistors 8 and 9 are substantially independent of temperature. If the electrical resistance of the resistor 8 or 9 has a weak dependence on the change of the environmental state, this change is preferably a detection opposite to the change of the resistance of the sensor element 7. For example, if the sensor element 7 is an NTC thermistor, the resistors 8 and 9 that are substantially independent of temperature have a weak positive temperature coefficient resistance. That is, their resistance can increase slightly with increasing temperature, but this change is significantly less than that of the sensor element 7 and is preferably at least an order of magnitude smaller.

  Preferably, the resistor 8 and the resistor 9 are also integrated in the analog circuit 1 similarly to the sensor element 7. For example, when sensor element 7 is printed, as described in US Pat. No. 9,029,180, resistors 8 and 9 are printed in a similar manner using a suitable resistive ink composition. Can be done. Alternatively, one or more resistors 8 and 9 may be supplied as additional components that are attached to and connected to the analog circuit 1 via connection pads.

  When a potential difference or voltage is applied to the analog circuit 1 via the external connection 6 or a current flows through the analog circuit 1, two or more potentials are integrated via the conductive pattern 3 and the connection pad 4. 5 is applied to the input terminal 10. One of these potentials corresponds to the measurement condition to be determined, for example temperature, and the other second potential is the internal reference value, for example the total potential difference applied to the sensor and one or more resistors. Corresponding to The integrated circuit performs various operations internally before supplying a unique digital signal to one or more output terminals 11 that clearly corresponds to a combination of two or more potentials applied to its input terminals. be able to.

  In a preferred embodiment, integrated circuit 5 is a microcontroller or microprocessor having at least two analog inputs. These inputs may be internally connected to independent analog / digital conversion (ADC) channels or multiplexed into a single ADC. Alternatively, additional integrated circuits may be attached to the analog circuit as an input stage to the microprocessor or microcontroller. As an example, one or more independent ADCs may be connected to the digital input, or a multiplexer may be used as the input stage for a single analog input. It may be further desirable to combine an independent multiplexer and a single ADC together as an input stage to the digital input of a microcontroller or microprocessor.

  Although it is possible to use only a multiplexer and ADC so that the digital output of the ADC is connected to the output terminal, this is not desirable. However, this embodiment is not preferred because the use of a microcontroller provides additional functionality for the entire component. This functionality is provided by the ability to perform additional calculations on the sensor data to provide calibrated numerical values. This may be as simple as calculating the ratio of potentials applied to the analog input terminals. Alternatively, a calibration function can be applied to estimate changes in actual values or monitored environmental conditions. For example, in the case of a temperature sensor, the actual temperature may be output on a selected temperature scale such as Celsius or Fahrenheit.

In the preferred embodiment, the values calculated and output by the integrated circuit are transmitted in serial form via one or more output terminals. Any industry standard protocol may be used including, but not limited to, SPI, I ² C, UART, 1-wire, 2-wire, 3-wire, and the like. In another preferred embodiment, multiple output terminals are used simultaneously to transmit numbers in parallel format, one terminal corresponding to one bit of information, the information including control characters and text labels and numbers. Also good.

  In the further preferred embodiment shown in FIG. 2 attached, a further integrated circuit 12 comprising a non-volatile memory is attached to the substrate 2. Integrated circuit 12 is connected to one or more digital input / output terminals of integrated circuit 5, which is preferably a microcontroller or microprocessor and forms the digital portion of the overall circuit. The connection between the two integrated circuits is preferably integrated into the conductor pattern 3 used in the analog part of the circuit. Connections between the digital input / output terminals of two integrated circuits can be facilitated using either serial or parallel data formats in a manner similar to data transfer to external connections.

  An internal battery (or cell) 13 may be mounted opposite the external connection used to supply power from an external power source so that the sensor and microcontroller function autonomously with any external connection. In this way, the component can function as a data logger as well as a sensor. Ideally, the battery 13 is a rechargeable battery, but electrolytic capacitors, supercapacitors, primary cells, photovoltaic cells or other potential sources may be applied as well.

  The hybrid electronic sensor of any of the above embodiments can be connected to additional electronic circuitry via external data and power connection 6 to form a complete sensing system. For example, as shown in FIG. 3 of the accompanying drawings, the integrated circuit 5 can communicate its data to the wireless transceiver 14 using a serial or parallel data protocol. The power connection to the antenna 15 and the transceiver may be further incorporated into the analog detection circuit 1 formed by the conductor pattern 3 on the same substrate 2. If a rechargeable battery 13 is also provided, energy may be recovered from the radiated field to provide power to the sensor and integrated circuit.

  The invention will be further described with reference to the following non-limiting examples.

(Example 1)
FIG. 4 shows a photograph of a hybrid electronic digital temperature sensor configured according to the first embodiment shown in FIG. The completed component is assembled on a layered PET sheet that functions as the substrate 2 and has a total thickness of about 0.25 mm. The conductive pattern 3 including the interconnecting portion, the connection pad 4 and the external terminals 61 to 66 uses silver-based ink, like the internal electrode structure of the NTC thermistor 7 and the resistors 8 and 9 which are substantially independent of temperature. The film is formed by screen printing. Many suitable compositions are readily available, for example, DuPont 5000 silver conductors are used in the examples presented here.

  The integrated circuit 5 used in this example is an 8-bit microcontroller in an SOP-8 package that has the same footprint as the SOIC-8 package. In this embodiment, the microcontroller is an Atmel 85 ATtiny 85. The integrated circuit is attached to the connection pad 4 using a conductive adhesive. External connection is made through six terminals 61 to 66 as follows. Reference numeral VCC is negative power supply voltage or common zero, reference numeral VSS is positive power supply voltage not exceeding the specification of the microcontroller, reference numeral 63 is serial digital transmission Tx, and reference numeral 64 is serial digital transmission. The receiving Rx, and reference numeral 65 is a chip select. Alternative configurations of master output / slave input (MOSI), master input / slave output (MISO), and terminals 63-65 as external clocks may also be applied.

  NTC thermistor 7 and substantially temperature independent resistors 8, 9 are described in US Pat. No. 9,029,180 and PCT Publication No. WO201311289, incorporated herein by reference, Manufactured by screen printing directly on the printed silver pattern. As shown in FIG. 1, these three resistors are connected in series and have the same power supply as the microcontroller. The intersection of the thermistor and each resistor is connected to two input portions of the microcontroller 10 configured as a 10-bit ADC through the connection pad 4 by the conductor pattern 3. Thus, the input to the microcontroller includes independently measuring the potential difference across resistor 9 and the combined potential difference across resistor 9 and thermistor 7. The ratio of these two potentials provides a unique measurement of the temperature experienced by the sensor. Using a calibration function stored in the microcontroller, this ratio is converted to a temperature value on an appropriate scale.

Claims (10)

An electronic detection component that provides digital output in response to quantifiable changes in environmental conditions,
An analog circuit in which at least one detection element whose resistance changes in response to a change in environmental conditions is integrated;
At least one other resistor whose resistance remains constant as environmental conditions change;
And at least one integrated circuit,
The analog circuit and the integrated circuit are connected such that when a potential difference is applied to the analog circuit, two potentials are applied to the input terminals of the integrated circuit,
One of the two potentials corresponds to the measured environmental condition, the other of the two potentials corresponds to a reference value,
Generating a unique digital signal at one or more output terminals of the integrated circuit;
The unique digital signal corresponds to a change in the measured environmental condition;
Electronic detection parts. The detection element is a thermistor having a negative temperature coefficient, and the resistance of the thermistor decreases as the temperature increases.
The electronic detection component according to claim 1. At least the thermistor and wiring of the analog circuit are made by printing,
The electronic detection component according to claim 2. Two resistors of constant value are connected in series with the sensing element,
The two potentials applied to the input of the integrated circuit are respectively a potential difference across one of the resistors having a constant value and a potential difference across the resistor and the sensing element having a constant value.
The electronic detection component according to claim 1. One or more potentials are applied to an independent analog-to-digital converter or a single analog-to-digital converter via a multiplexer,
The electronic component of any one of Claim 1 to 4. The integrated circuit comprises a microcontroller or microprocessor that performs additional calculations on the data before providing digital values to one or more output terminals.
The electronic component of any one of Claim 1 to 4. Digital output is provided via serial interface,
The electronic component according to claim 6. Digital output is provided through a parallel interface that uses multiple output terminals simultaneously,
The electronic component according to claim 6. The output of one integrated circuit is connected to a second integrated circuit having a non-volatile memory,
The electronic component according to claim 7 or 8. The microcontroller is connected to or integrated with a radio transceiver integrated circuit, and an antenna is connected to or incorporated in the analog circuit.
The electronic component according to claim 6.

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